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LO 8-13 Outline the scope of cylinder block service and describe common service operations

Site: CDX Learning Systems
Course: DE Section 2-1: Engine Blocks and Cylinder Heads
Book: LO 8-13 Outline the scope of cylinder block service and describe common service operations
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Date: Thursday, 5 November 2026, 7:50 PM

Table of contents

1. Cylinder Block Service

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Cylinder Block Service

Diesel engine block service requires a high degree of skill and knowledge due to the sophisticated and exacting precision fit of components, such as liners, pistons, cylinder sleeves, and bearings. Little margin for error is permissible, and mistakes in fitting closely machined tolerances or failure to follow acceptable service procedures can result in costly, catastrophic engine failures. A major operation during engine overhaul and rebuild is cylinder liner removal and installation. A variety of tools are used to pull liners and/or complete liner and piston assemblies from the engine block. Similarly, the tools used to reinstall and correctly adjust the height or protrusion of liners above the block deck must be those prescribed by the manufacturer to deliver consistent quality of reliable repairs and ensure trouble-free engine operation.

 

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1.1. Video: Removing a Liner

LO 8-13 Video: Removing a Liner

 

 

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1.2. Liner-to-Cylinder Block Fit

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Liner-to-Cylinder Block Fit

The fit of a liner into the cylinder block is critical to engine operation because it can produce various leaks and cause premature (or even catastrophic damage) to cylinder components, such as pistons and rings. For example, a dry liner with an excessively loose fit will not transfer heat to the cylinder block as effectively as a liner that fits correctly. Cylinder heat will build up and cause scuffing, scoring, and eventual seizure of the piston. An excessively tight-fitting liner will collapse and distort, reducing the piston-to-liner clearance and causing hot spots. Consequently, the piston and liner can become scored, which could lead to eventual failure.

In wet liners, interference fit between the top-stop flange and the counterbore, or the lower part of the counterbore, is a coolant seal. A loose fit will allow coolant to leak above the block deck or into the cylinder.

 

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1.3. Video: Measuring the Cylinder Bore

LO 8-13 Video: Measuring the Cylinder Bore

 

 

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1.4. Piston-to-Liner Sleeve Fit

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Piston-to-Liner Sleeve Fit

Adequate piston skirt clearance must be maintained between the liner and the piston to allow for normal expansion of the piston when running at operating temperature. Insufficient skirt clearance will reduce the running clearance and could lead to scuffing or scoring. Excessive clearance will result in piston knock or slap. To measure the clearance between the piston and the cylinder wall, the largest thickness of a feeler blade is slid between the skirt and the liner at 90 degrees to the wrist pin. A typical specification in a 10–15 L (610–915 in 3 ) engine is 0.004–0.006" (0.102–0.152 mm) clearance.

 

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1.5. Liner Protrusion

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Liner Protrusion

Wet liners protrude or extend 0.001–0.01" (0.025–0.254 mm) above the cylinder block deck Figure 90. This extension is necessary to project clamping forces from the cylinder head onto the liner flange and hold it in place. Measuring and adjusting protrusion is one of the most critical operations when rebuilding a sleeved engine. In most engines, variations between individual liner protrusions must be no more than 0.002–0.005" (0.051–0.127 mm) between the highest and the lowest liner. Liner flanges must also be perfectly parallel with the block deck, typically within 0.001–0.002" (0.025–0.051 mm). Problems with the liner flange or counterbore or a twisted O-ring will tilt a liner. The liner must be removed and reinspected before reinstalling.

A liner must be clamped into place after installation in order to measure protrusion Figure 91. After installing and correctly tightening hold-down clamps on engine block liners to specifications, a dial indicator on a sled is used to measure the projections Figure 92. When placed on the block deck, the dial indicator depth gage is set to 0. The depth gauge is then moved to the liner flange and its height above the block deck is measured. Three or four points around each liner are measured and recorded. After all liners are measured and no defects are found, the hold-down clamps can be removed.

   Fig08_90

FIGURE 08-90: Liner protrusion is the projection of the liner flange above the block deck.

 

  Fig08_91

FIGURE 08-91: Liners need to be clamped in place before measuring protrusion.

   Fig08_92

FIGURE 08-92: Liner protrusion is measured by comparing the block deck height to the height of the liner flange.

  

 

Note that if one liner is slightly lower than adjacent liners, a leak path for combustion gases and coolant can form. If the variation is great, it might even warp the cylinder head. Variation will cause liner movement, which will damage both the counterbore and the cylinder head. If one liner is slightly higher than the others, it will have the same result of leakage and warpage. The liner will not move, but the concentration of cylinder head clamping forces on the higher liner can crack the flange. If protrusion is very high, tightening the cylinder head over the liner could warp and even crack the cylinder head.

 

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1.6. Counterbores and Liner Protrusion

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Counterbores and Liner Protrusion

Ensuring that cylinder liners protrude or extend above the block deck by the correct amount is one of the most critical operations for engine technicians. Without enough protrusion, a liner can move in the block, resulting in rapid wear, leaks, and block damage. If there is too much protrusion, the cylinder head gasket cannot seal properly. Uneven protrusion between liners results in compression and coolant leaks, cracked liner flanges, liner movement, and warped cylinder heads. Liner counterbores or ledges (where the liner sits in the block) must be carefully inspected before liners are installed to ensure that they are square and cut to the correct depth. The counterbore may need to be shimmed if liner protrusion is too low or cut and shimmed if the liner sits too high and the counterbore is damaged in any way. Anytime a liner is installed, the protrusion must be measured. Liner counterbores can be repaired with cutting and machining. A liner with inadequate protrusion can be raised with the installation of a shim beneath the liner flange Figure 93.

  Fig08_93

FIGURE 08-93: A liner with insufficient protrusion or a block that has a machined counterbore can be raised with a shim beneath the liner flange. Shim thickness is calculated after measuring counterbore depth, liner flange, and desired protrusion.

  

 

Top-stop flange breakage is usually caused by excessive flange loading because of significant pressure that was applied to the flange through the cylinder head clamping forces. The cylinder head gasket distributes a large amount of clamping force over the block deck, but if it is accidently left uninstalled when the cylinder head is tightened, all the liner flanges will crack and break due to the localized clamping forces. Flange breakage can also result from the following conditions:

  • Improper torqueing of the cylinder head during a rebuild
  • Uneven flange height above the deck
  • Uneven wear in the cylinder block flange counterbore if liners are not uniform in protrusion or are not parallel to the block deck
  • Worn inner edge of the flange counterbore seat (in the cylinder block), causing the flange to tilt downward
  • Improper positioning of the head gasket fire ring

To measure liner protrusion, follow the guidelines in Skill Drill 8-2.

 

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1.7. Video: Measuring Counterbore Depth

LO 8-13 Video: Measuring Counterbore Depth

 

 

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1.8. SKILL DRILL 8-2  Measuring Liner Protrusion

SKILL DRILL 8-2  Measuring Liner Protrusion

 

STEP 1
Inspect the liner counterbores for squareness, cracks, and the correct machined depth. Generally, the machined depth is only measured if there has been a problem with protrusion or the counterbore has been machined.

STEP 2
Thoroughly clean the liner and counterbores. Any dirt or other material will prevent the liner from seating properly.

STEP 3
Install and lubricate the liner seals. Seals are lubricated only after they are installed (in order to prevent twisting and rolling when the liner is installed). Slide a small pick beneath the O-ring and move around the liner circumference several times to make sure that the ring is not twisted. Generally, seals are not lubricated with petroleum-based products; this prevents rapid deterioration if the seals are not oil compatible. Antifreeze is often used as an effective lubricant.

STEP 4
Insert the liners into the engine block. Do not force the liners into the block. Instead, use the OEM-prescribed tool to press the liner into the block. Hammering or hitting the flange can dent the flange surface, which causes a leak path. The OEM-prescribed tools will protect the liner flange and sealing surfaces from damage. They can be used to install the liner squarely into the block and, in some cases, clamp the liner into the block.

STEP 5
Clamp the liner in the block with the OEM-prescribed holding or clamping fixture, following the manufacturer’s procedures.

STEP 6
Measure the liner protrusion in three or four places using a dial indicator and sled. Protrusion is measured as the distance between the block deck and a very specific point on the flange; this point varies between manufacturers.

STEP 7
Compare the measured protrusion against the manufacturer’s specification values. Variation from side to side should not exceed 0.001" (0.025 mm). If it does, it is usually due to a piece of debris beneath the flange or a twisted O-ring. Remove, check, and reinstall the liner if the liner variations are excessive from side to side. Install a selective shim beneath any liner flange that sits too low.

 

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1.9. Maintenance of Cylinder Walls and Bearings

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Maintenance of Cylinder Walls and Bearings

Cylinder walls and engine bearings are the two areas that have the highest degree of wear; as a consequence, they are the most significant factors limiting engine service life. For this reason, servicing and maintaining these two parts of an engine are commonly performed during major and minor overhauls. It is important for technicians to understand the factors influencing wear to anticipate features of these areas to inspect. Understanding wear factors helps to form a foundation for service practices.

Cylinder Wall Wear
Diesel engine cylinder walls last longer than their gasoline counterparts for several reasons. First, slower engine speeds reduce the amount of piston travel. Second, diesel fuel acts like a lubricant to minimize wear from friction. Third, cylinder block and liner hardening processes and the use of special alloys further increase the durability of diesel blocks. However, cylinder block walls progressively wear with increasing engine hours and distance traveled. The greatest amount of wear occurs near the uppermost part of the compression ring travel path and diminishes down the cylinder to the bottom Figure 94. This gives a worn cylinder a bell-shaped wear pattern observed at the top of the cylinder sleeve. The reasons for the greatest amount of wear near the top of the cylinder wall causing the cylinder wall to taper include the following:

  • Higher cylinder pressures near the top part of the piston’s travel path increase ring pressure against the cylinder walls because gas pressure behind the rings forces the piston rings outward from their grooves.
  • Higher cylinder temperatures make the cylinder wall softer and more prone to wear.
  • Lack of upper cylinder wall lubricant because lubrication oil can only be carried into this area on the face of the compression ring.

Long-stroke engines will have more wear mid-stroke due to a higher amount of major thrust. The side thrust is produced by the angle of the connecting rod with the piston, which tends to push the piston sideways into the cylinder wall when cylinder pressures are high. The angle formed between the connecting rod and the piston forces the piston against the cylinder wall during the compression and power strokes. The force is greatest during the power stroke, producing a major thrust force and a minor thrust force during the compression stroke. The longer stroke distance of the diesel makes for higher thrust angle forces Figure 95. In heavily loaded engines, wear is greatest at mid-stroke, when piston velocity and connecting rod angles are highest. To measure cylinder wall wear, follow the steps in Skill Drill 8-3.

To visually evaluate cylinder wear, follow the guidelines in Skill Drill 8-4.

  Fig08_94

FIGURE 08-94: Cylinder wall wear is tapered and greatest in the upper third of the cylinder. The lack of upper cylinder wall lubrication combined with higher cylinder wall temperatures and ring pressure produce the greatest cylinder wear in this region.

   Fig08_95

FIGURE 08-95: Cylinder wear at mid-stroke is a common condition in engines with high thrust forces.

  

 

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1.10. Video: Replacing Main Bearings

LO 8-13 Video: Replacing Main Bearings

 

 

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1.11. SKILL DRILL 8-3  Measuring Cylinder Wall Wear

SKILL DRILL 8-3  Measuring Cylinder Wall Wear

 

Several methods can be used to measure the amount of taper within a cylinder.

  Fig6_01   Fig6_01  

 

STEP 1
Measure the amount of piston ring end gap in a cylinder. By measuring the end gap at the top of the cylinder, in the ring turnaround area, in the middle, and at the bottom, cylinder taper can be calculated. End gap is measured after squaring the ring with a piston inside the cylinder. A 0.001" (0.0254 mm) increase in cylinder wall diameter will produce approximately a 0.003" (0.0762 mm) increase in ring end gap. A typical maximum taper wear of a cylinder is 0.001" (0.0254 mm) per inch of cylinder diameter, up to 0.005" (0.127 mm) maximum wear in larger cylinders.

STEP 2
Look for loss of crosshatch. Cylinder crosshatch is produced when an engine is manufactured and during reconditioning. The presence of crosshatch on the cylinder wall is important to provide a surface to seat piston rings and to retain oil for piston and ring lubrication. Highly polished liners will not allow residual oil to cling to the cylinder walls, causing scuffing and piston wear. Highly polished liners indicate worn cylinders.

STEP 3
Use a dial bore gauge to measure cylinder taper but not cylinder diameter. These gauges are used when honing or performing other machining processes to ensure that a consistent, symmetrical dimension is produced.

STEP 4
Use a micrometer and inside telescoping gauges. An inside telescoping gauge is used to gauge the cylinder diameter. An outside micrometer is then used to measure the width of the inside telescoping gauge.

 

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1.12. SKILL DRILL 8-4  Visually Evaluating Cylinder Wear

SKILL DRILL 8-4  Visually Evaluating Cylinder Wear

 

  Fig6_01  

 

One effective method to visually evaluate cylinder wear is to examine the ring turnaround area.

STEP 1
Measure the length of the missing crosshatch worn away by the top ring by using a piece of white paper to reflect light directly into the crosshatch.

STEP 2
Measure the stroke length of the cylinder and compare it to the length of the missing crosshatch area.

STEP 3
If 20% or more of the crosshatch is missing, 0% service life remains. If 10% of the crosshatch is missing, 50% service life remains. An engine with a 5" (13 cm) stroke and 0.25" (6 mm) of polish has 75% service life remaining.

 

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1.13. Bearing Failures

LO 8-13: Outline the scope of cylinder block service and describe common service operations.

 

Bearing Failures
Most bearing failures are caused by problems with lubrication Figure 96. Bearing failures are indicated by:

  • A drop in lubricating oil pressure
  • Excessive oil consumption (excessive oil thrown onto the cylinder walls)
  • Noise levels of knocking sounds that are reduced during a cylinder cut-out procedure

Bearing roll-ins are performed during engine overhaul. Because the crankshaft is not removed when the engine is repaired in chassis, the upper main bearing shell must be pushed out and another bearing rolled into position.

   Fig08_96

FIGURE 08-96: Causes of bearing failures.

 

Measuring Crankshaft End Play
Occasionally, crankshaft thrust bearings may become excessively worn or even broken. A sudden, sharp release of the clutch or a driver’s foot resting on the clutch can apply excessive force against the thrust bearing, leading to premature wear or breakage. The result is a slipping clutch or difficulty adjusting a clutch, with the free play continually changing after a manual adjustment. Crank position sensor fault codes may also be logged if end play is excessive. Insufficient end play can be the result of a misaligned main bearing cap.

To measure crankshaft end play, follow the guidelines in Skill Drill 8-5.

 

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1.14. SKILL DRILL 8-5  Measuring Crankshaft End Play

SKILL DRILL 8-5  Measuring Crankshaft End Play

 

STEP 1
Place a dial indicator magnetic base on the engine block. Place the needle indicator on the vibration damper.

STEP 2
If the vehicle is equipped with a manual transmission, push on the clutch. With the clutch depressed, zero the dial indicator. Alternatively, a pry bar between the flywheel and the flywheel bell housing inspection hole can be used to pull the flywheel rearward.

STEP 3
Push the flywheel forward using a pry bar between the flywheel and the inspection hole in the flywheel housing.

STEP 4
Observe and record the measurement on the dial indicator. Specifications are generally in the range of 0.004–0.019" (0.102–0.483 mm). The specifications may seem large, but bearing clearances must be wide enough to allow oil to flow on both sides of two thrust washers or bearing flanges.

STEP 5
Make service recommendations to inspect and replace the thrust bearings or remove the oil pan and perform further inspection of the engine.

 

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